Sifter



Feb. 5, 1929.

S. SCHIFF S IFTER Filed Feb. 23, 1926 2 Sheets-Shen 7 2 6% 79 44 x y-: /a au 3- 0l. z-. M 7.

glwuenfoz 'fgmund Qcmff,

S. SCHIFF Y Feb. 5, 1929.

SIFTER Filed Feb. 23'.' l1926 Inventot 'igmund chi'ff,

Patented Feb. 5, 1929.

UNITED STATES SIGMUND SCHIFR F CINCINNATI, OHIO,

SIFTER.

Application filed February 23, 1926. Serial No. 89,956.

This invention relates to sifting mechanisms and is adapted for efficiently sifting all kinds ot pulverized substances.

An objecto't' my invention is to provide a device for the purpose stated which is rapid in operation and one which will accurateiy grade a siitable substance, and deposit the siited substance and tailings in separate containers.

Another object is to provide a device of this lrind which is ope 1able through combined mechanical means and air pressure means.

` These and other objects are attained by the means described herein and disclosed in the accompanying drawings, in which:

Fig. l is a side elevational view of a device of my invention shown partly in cross section.

Fig. 2 is a view taken on line 2-2 of Fig. 1.' v

Fig. 3 is a plan view ot a combined air brush and scraper forming a detail oi my invention. y

Fig. 4 is a view taken on line 4-4 of Fig. 1.

Fig. 5 is a cross sectional view taken on line 5-5 of Fig. y

F ig. 6 is a cross sectional view on line (1i-6 ot' Fig. 1.

Fig. T is a side elevational view looking runwardlyon Fig. 3.

The present invention comprises a pneu- 1 matic sifting device arranged to obviate d1sadvantages heretofore encoi'lntered devices ot this hind. The device generally comprises a hopper having adjustable discharge per- At'oi'atious "for regulating the feed of the substance to be siftcd into the pneumatif.'y sitter and this hopper `is provided with agitating means insuring an even 'ate of feed. The sittable substance is ted into a pressure sitting chamber having a bottom mesh of the desired degree oil tineness of the substance to l t i 1 Disposed Within this pressure :er is a means tor effecting even x area of sitting mesh or screen and this means 'furthermore serves to help build up air pressure in the sitting chamber tor forcing the particles of a given size throughthe screen or mesh. In order to preclude the screen or mesh from becoming clogged with siftable substance, there is provided a moving air brush or agitator which progressivelyT raises the sittable substances trom the entire area of the screen and serves to place` all oit the substance in suspension in order that it may be driven through the clearedportion ofthe screen by the air pressure and at the same time to elfectively move the tailings or undesired portion ci' said siftable substance to a port through which it may discharge into a tailing bor; or hopper. The air brush just described moves in an expansion chamber which is provided with means for retaining a lower pressure than that in the sifting chamber, and this air brush is provided with means for moving all of the sifted substance to a given port through which it may pass into a suitable container`- In the embodiment hereinafter described, the pneumatic distributor and air brush and scraper are all actuated from a singie shait't connected to a suitable source of pou'er. A blower fan serves to build up the necessary pressure for the air brush and sitting chamber and is so arranged in connection with the expansion chamber that` practically allot the light sifted substance is discharged directly from the expansion chamber into a receiving container and any portion which may remain in suspension may be removed by passing the dust carrying air through a dust collector of any approved type before the air returns to the fan :from whence it is again blown into the sifting chamber. The device comprises a supporting frame comprising uprights l() and cross members 11 which may take the Yform of angle irons, suitably secured one upon the other. The cross members 11 may extend foradistance beyond the uprights at one side of the 'frame in `order to accommodate a unit comprising a blower fan 12 and motor 13. ltlounted upon the uprights 10 is a casing 14 which may be conveniently andeconomically formed square in plan and made of sheet metal and this chamber constitutes the body and sidewall portion of expansion chamber 1,5 within which are disposed the sifting chamber 16, air brush 70, and distributor mechanism. The sifting chamber 16 comprises a frame having side Walls 17,the bottom edges otl which have secured thereto a sitting mesh or screen 18`Which may be of Wire gauze or silk and having a mesh of such.

i size as to permit passage of the particles to he sifted and to preclude passage of the tailings or undesirable matter. The casing 14 is provided with a fianged apertured Cover 19, the flange 20 of which serves to seat the flanged edges of the side 17 of theisifter chamber. Packing strips 21, of felt or other suitable `nnueral may beinterposed :tu order to preclude passage of the siftable substance from the sifter chamber or expansion chamber. Lid 22 for the sifter chamber 16 may be hingedly mounted upon the cover 19 and is centrally apertured for receiving a hopper 23. A. feed regulator serves as a base for the hopperl 23 and comprises a plate 24 rotatable with the hopper and having several rows of perforations 25 drilled therethrough, preferably disposed in staggered relation, and a casting 26 having a disc portion 27 perforated in the same manner as the plate 24. From the foregoing, it will be apparent that a maximum feed will be obtained when the perforations are in complete registry with the perforations 28 in the disc 27 and that as the hopperl 23 and plate 24 are rotated, the feed opening through perforations 25 and 28, will be reduced. Any suitable means, (not shown) may be provided in order to conveniently regulate the feed from the hopper. The casting 26 is lined and has a peripheral shoulder 29 extending about the edge of the disc portion 27 thereof in order to mount the casting and hopper over the central aperture in the lid 22. Casting 26 has a central boss 36 having a bore therethrough. A bearing 31 mounted in the bore of the boss supports a short shaft 32 to which is pinned an agitator 33 having an arm 34 adapted to travel adjacent the inner wall of the hopper 23 for insuring the downward feed of the substance to be sifted onto the plate24. The agitator 33 may also be provided with a brush 340 which sweeps over the perforations in' the plate 24 in order to insure uniform movement of the siftable substance through the perforations. The lower end of the shaft 32 carries a brush bracket 320 having rectangular blocks or keys 35 and serves to impart motion of the distributor, herein after described, to the agitator in the hopper. The collar port-'ion 36 of bracket 320 is provided with suitable arms 37 which carry brushes 38 and 39. Brush 39, revolving with shaft 32, removes siftable substance from the undersideof the feeder, and is followed up by brush 38 which moves such substance into the path of an air current for distribution over screen 18. The distributing means comprises a. revolving feeder nozzle 41, revolving brushes 38 and 39, and a ring-like distributor plate 40 which carries a dellector plate 42. Plate has the form of a shallow truncated cone of sheet metal having a central Iaperture 43 to accommodate the connection between keys or blocks 35 on the collar 36 and a transverse slot 44 on nozzle 4l for turning shaft 32 and agitator 33. The plate 42 is secured to distributor plate 40 by any suitable means such as U-shaped members 45 disposed therebetween. The lower free end 420 of plate 42 is spaced slightly from the upper face of plate 40. Thus it is apparent that air directed outwardly by the revolving feeder nozzle into the annular discharge opening between deflector plate and distributor plate will be forcibly ejected therefrom to blow the siftable substance over the screen 18. The plates 40 and 42 are supported in side the sifter chamber and below the feed regulator by radially extending rods or support members 46 secured to the plate 40 and the sides 17 of the sifter chamber. Rings 47 and 48 bound a central opening 51 in screen 18, serving to secure therebetween the edges of the screen at the opening. Ring 48 is U-sliaped in cross section, the channel thus formed being used to form a dust tight connection between it and a rotatable cylinder 480. lt is apparent that cover 22 with the complete feed regulator and brushes 38 and 39 may be lifted as a unit. Likewise, the sifting chamber comprising sides 17 screen 1,8, rings 47 and 48 and plates 46 and 42 with support members 46, may be removed as a unit. The cylinder 480 is secured at its lower edge to a bearing flange 49 rotatably mounted upon a stationary supporting member 5() which is secured about a central opening 51() in the bottom of the casing 14. The bearing flange 49 forms the lower bearing portion of a combined brush holder and feedernozzle.

The combined brush holder and feeder noz-A zie comprises an integral casting including` the bearing flange 49 and bearing 'flange 52 concentric therewith and connected thereto by spaced webs 53 providing communication between the interior of the cylinder 486 and the floor member 54 of the support casting 50. The casting has its central upper portion developed into a tubular member upon the end of which may ride the shouldered flange 52 of the brush holder and feeder nozzle member. The floor member 54 of the casting 50 has an openingl 56 therein surrounded by an annular flange 57 which may be connected to a tailing box housing 58. The brush holder and feeder nozzle is a hollow casting having two discharge openings 59 and 60 disposed at substantially rightangles to its intake opening 61 which ,is bounded by the flange 52. The opening 59 registers with an opening 62 in the cylinder 480 and about which opening the cylinder is secured to the brush holder and feeder nozzle member. The feeder nozzle 41 provided with a disc-like section of metal dife posed below its discharge opening and this disclike portion of metal rotates in the central aperture in stationary distributor plate 40 and forms a seal for said aperturi'i. The top of the feeder nozzle 41 is provided with a transverse slot 44 in which the keys or blocks 35 on the collar 36 may seat. From the fore going it will be apparent that when rotary motion is imparted to the brush holder and feeder nozzle, the cylinder 480 will rotate and the agitator 33 and brush 340 will all partake lOO of the movement. of the brush holder and feeder nozzle. An actuating shaft has a bearing in a tubular offset 66 in the lower portion of thecasting 5() and extends through the hollow interior of castinv 50 and also through the interior of the brusli holder and feeder nozzle casting which is secured to saidsliaft by any suitable means such as a pin 67. Rotatory movement is imparted tol the shaft 65 from any suitable power source, such as a pulley 68 by means of meshingbevel gears 69.` As shown in Fig. 1, an air brush 70 is secured tothe cylinder 480 and theopening 62 in the cylinder provides communication between the interior of the brush holder and feeder nozzle casting and the hollow interior of the air brush 70. The air brush 76 is provided with a longitudinal air discharge slot 71 which extends radially of the cylinder 480. Interiorly of the air brush is an elongated and substantially flat channel 72, the upper portion of which is restricted by convergingly disposed walls 73 which form the discharge slot 71. A baille plate 74 is secured interior-ly of the air brush IOand extends from the opening 62 for a distance toward the free end of the air brush. The baille plate 74 serves to alter the direction of flow of air pressure from the air brush as well as to substantially equalize suoli flow throughout the length of the discharge slot 71. In other words, it directs the incoming air from opening 62' upwardly and radially inwardly through discharge slot 71 instead `of allowing it to take a generally upward and radially outward movement as it would do if the baffle plate were omitted. The casting 50 has an opening surrounded by a lip 'To to which is secured a pipe 7 6" which serves to place the blower fan 12 in communication with the interior of the casting 50.

As shown in Figs. 1 and 4, an exhaust pipe 77 providescommunication between the upper portion of expansion chamber 15 and a dust collector 78 of `any suitable type. The dust collector may be interposed in the exhaust pipe line, which is in such instance connected with the tan,` as shown herein. The dust collector may take Jthe form of a porous bag which will permit escape of air but it will retain any other sifted substance which may by any chance, remain in the air. The pipe 77 has a fresh air intake opening 78 disposed adjacent theblower 12. Avalve 7 9 disposed adjacent the fresh air opening 7 8 provides a simple and very efficient means for regulating and maintaining the desired difference betweenthe pressure in thesifter chamber and the expansion chamber, the purpose of which will be more fully described hereafter. It should be noted, however, that this machine would operate with only a dust collector'and no return pipe to fan.`

An opening 8O disposed adjacent one corner of the bottom Wall of the casing 14 of the expansion chamber is surrounded by an annular flange 81 upon which may be slidably secured a receiving container of any desired form (notshown). A scraper 82" has its one end secured tothe outer en-d of the air brush 70 and its opposite endto the cylinder 480 and is so curved as to move the powder or siftable substance upon the floor of theexpansion chamber 15 before it and also to work` the substance outwardly so that it may drop through the opening into a receivingcontainer.` A strip 8f3, which may be of leather, is carried by the lower edge of the scraper 82 in order to scrape all of the sifted substance free of the floor of the expansion chamber as the scraper moves over the surface thereof. i

In the structure just-described it will be noted that the central portion ofthe sifting chamber 16 or any portion below the distributor plate 401s in open communication,with

the interior of the cylinder 480, the lower portion of which is also in communication with the tailing box housing 58. It will also be noted that pneumatic pressure `from the fan 12 may move through pipe 76, through casing 55, and into the brush holder and feeder' nozzle cast-in g through the opening 61 from whence it may pass through the openy ing 59 to the air brush 70 and alsothrough the nozzle 41 where it will direct `its blast into. the space provided between the detlector plate 42 and the distributor plate 40. `.Since the expansion chamber 15 has an air outlet through dust! collector 7 8' and pipe 77, it will j;

be apparent that the pressure in expansion chamber will normally `be lower than the pressure in the siftingchainber 16. "This difference in pressure is also maintained through the action ofair brush 7 0 which directs substantially its entire discharge through the screen 4or mesh" 18 into thesifter chamber 16. By regulating" the rate of return flow through the pipe 77 by means of the valve 79, it is possible to regulate the difference in pressure between the sifting chamber 16 and expansion chamber 15 so that substantially all ofthe sifted-substanceor dust will drop to the floor of the expansion chamber from whence it will be scraped by the scraper 82 and pushed before said scraper until it drops through the discharge opening 81. `The opening 7 8 adjacent the blower fan 12 always permits an influx of fresh air so that even though the valve 79 be improperly j adjusted and thus permit some `of the dust to bedrawn through the pipe 77 from the expansion chamber 15, said dust and air will, by reason of its higher' pressure, lind prefi erence over the fresh air and pass into the" blower, pipe 76 and out through the nozzle into the sifting chamber where it willagain be acted upon.` It will be notted then that the opening 78 and valve 79 are very effect-ive for precluding double operation upon the sifted substance.

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Vparts rotatory motion to the agitator 33 and brush 340 which are rotated within the hopper and cause an even flow of the substance through the perlorations 25 and 28. The hopper with plate 2a having periiorations 25 `therein may be rotated for effecting the proper registration of pertorations 25 and 28 in order to attain the proper rate ot feed trom the hopper, as heretotore explained.

vThe sittable substance passes through pertevrations 25 and 27, onto the plates l0 and 12.

' Brush 38, being,r disposed immediately preceding' the nozzle 111 serves to place the substance to be sitted into the path oi the blast of air 'from nozzle 4J, which blast of air scatters the siftable substance out into the sitter chamber 16 and deposits it evenly over the surface of the screen or mesh 18. The rotation ot' the nozzle 4l serves to distribute the substance over the entire area ot the screen or mesh 18 and at the same time serves to help build up air pressure in the sitting chamber as does also the brush 70. As the pressure linde its way out of the sifting chamber through the screen or mesh 18, it carries with it such particles of the sittable substance as will pass through the mesh ot the screen 18. It will be apparent however, that the desired substance will be placed momentarily in suspension and will find its way through the mesh ot' the screen only when the screen is practically clear and that as the tailings accumulate over a given area of the screen, the screen will become partially clogged and preclude ready passage or' the desired substance therethrough. The air brush TO, as heretofore explained, rotates as a unit with the ieed nozzle al and the discharge slot 71 of the air brush is disposed within the eX- pansion chamber and has its air discharge slot 71 immediately adjacent the lower face ot the screen 18. The air brush 70 extends radially of the center ot the shaft and is disposed on the side opposite the opening 60 in the feeder nozzle 11. As the member rotates, the nozzle Ll1 will scatter the si'iitable substance over the screen at one side oit the sii'ter chamber while the air brush 70 is dischargine,` its blast through the screen at the oppositie side. rlhe blast through the slot 7l ot the air brush l'O directed diagonally upward and centerward along a radius drawn from the shaft 5 and this blast blows the sijltable subst-ance upwardly and inwardly away from the screen, thereby placing,r the linely divided particles momentarily in suspension within the sitter chamber and at the same time carrying the larger and heavier tailings centerward. As soon as the brush passes a `given area ot the screen and has cleared the sittable substance therefrom, the pressure in the sifting chamber will rush out through the cleared portion of the screen and carry with it the finely divided particles to be silted. As the air brush and feeder nozzle rotate, it will be apparent that the screen 18 is progressively covered with sittable substance, part ot it will pass immediately through the screen 18 and that at the same time, the air brush will progressively clear the screen oi' the siflitable substance and tailings which may become packed upon .it so as to permit the removal ot more ot' the silt able substai'ice. rlfhe tailings are worked centerward and will rind their way through the opening?,v 5l in the screen and through the rings 47 and et@ into the interior or the cylinder 480 and will drop between the several webs 53 onto the table portion 54: ot the casting 50. As the webs 53 are carried about by the rotation of the brush holder and :feeder nozzle, the tailings which have dropped between these webs are carried over the table tace 54: oit the casting; 50, until said tailings approach the opening 56 in the table portion 5d from whence they may drop into the tail ing box contained within the housing 58. It should be noted that the tailing box housing 58 is air tight andthat there will be 1naintained the same pressure within the tailing` box, interior of the cylinder 480 and the sitter chamber 16. For this reasonthe air blast does not affect the tailings but merely permits them to drop by gravity as they are moved centerward to the edge of the opening' 51 in the screen. Thus it will be seen that that portion of the siftable substance which is tine enough to be atlzected by the movement oit' air from the sifting chamber to the oxpan sion chamber will be carried through the mesh while the tailings will be worked centerward and will be acted upon only by the blast from the air brush and by gravity. In .p "acties, it has been found that proper adjustment of the 'teed from the hopper will cause a perfect separation of the sitted substance and tailings so that the tailings are tree from any of the desirable sittcd substance and the sifted substance is tree oit par ticles larger than the mesh ot the screen 18, As has been heretofore explained, the pressure in the expansion chamber is reduced by reason of the opening' 78 in the pipe TT so that when the iincly divided sittedA substance passes through the screen 18, it will drop to the floor of the casing),l 1a, and that very1 little other siiitable substance will remain in suspension in the expansion chamber long enough to be carried out. However, should the valve 79 be improperly adjusted, some ol said substance which may pass out of the cx.- pansion chamber into the dust collector may drop bach onto the floor of the casing 14., but that which may pass through dust collector till lll)

and pipe 77 will not be 10st, but will be carried back to the sitter chamber through the teed nozzle al. The scraper 82, shown in Figs. 3 and a, will partake ot the counter clockwise rotation ot the air brush and teed nozzle and will push betore it allot the sitted substance which drops to the floor ot the expansion chamber and at the same time will worl; said substance outwardly toward the end `ot the scraper so that the sitted substance may drop through the opening S0 into the container. This container` should, ot course, have an air tight connection with the ilange 8l surrounding the discharge opening S0 in order to prevent loss ot the sitted substance.

TWhat I claim is:

l. In a device ot the class described the combination ot an expansion chamber member,A l a sitter chamber member having a screened covered opening communicating with the expansion chamber, means tor teed-` ing a. sittable substance into the sitter chamber, pneumatic means tor depositing sittable substance trom the teeding means upon the screen within the sitter' chamber, an air brush disposed within the expansion chamber and adapted' to direct airnnder pressure through the screen into the sitter chamber, blower means tor supplying pneumatic pressure to the air brush and pneumatic depositing means, and means tor providing communication between the expansion `chamber and the` blower means tor-maintaining a given pressure in the sitter chamber and a lesser pressure in the expansion chamber whereby the sittable substance in the sitter chamber may be carried throughthe screen into the expansion chamber through the agency ot the movement ot air trom the expansion chamber to the sitter chamber.

In a device ot the class described the combination ot an expansion chamber', a sitter chamber having an open bottom in communication with the expansion chamber, a screen member tor said opening and having a central aperture therethrough, a plate in the sitter chamber and positioned above the central aperture in the screen, means tor def` positing asittable substance upon said plate, a teed nozzle adapted to blow the sittable substance trom the plate onto the. screen serving to building up pneumatic pressure in the sitter chamber, an air brush disposed Within the expansion chamber and adapted to direct a blast ot air through the screen into the sitter chamber, blower means tor supplying pneumatic pressure to the air brush and teeder nozzle, means tor maintaining a dilterence in pressure between the sitter chalnber and expansion chamber, and means tor impart-` ing rotatory motion to the air brush and feed nozzle.

In a device ot the class described the combination with a sitter chamber comprising a trame, lid, and abottom screen member having a central aperture therein, ahopper and teed device adapted to dischargea sittable substance into the sitter chamber, a plate inthe sitter chamber vtor receiving a sittable substance trom the hopper, pneumatic teed means tor moving the sittable sub-` stance trom the plate onto the screen, an eX- pension chamber communicating with the sitter chamber through the screen, an air brush in the expansion chamber adapted to direct an air blast through the screen into the sitter chamber, and serving to clear the screen ot sittable substance and to place the liner particles ot said sittable substance in suspension in the sitter chamber, blower means connected with the air brush and pneumatic feed means,nmeans tor establishing communica tion between the expansion chamber and the blower means and serving to cause movement ot air under pressure trom the sitter chamber to the expansion chamber and to substantially reduce the pressure in the expansion chamber, means tor imparting movement to the air brushand pneumatic teed means, a tailing` box, and means extending throughthe eX- pansion` chamber `and serving to" establish communication between the tailing box and that portion ot the sitter chamber disposed bcneaththe plate, the action ot the airbrush serving to direct its blast radially inwardly and upwardly toward theplate in the sitter. chamber tor permitting tailingsto drop by gravity into the tailing box. t 4.` Ina sitting `device the-combination ot a screen` member, means tor depositing `a sittable substance upon the screen,kan air brush adapted to direct air under pressure upwardly through the screen, and means for maintaining reduced air pressure beneath the screen wherebythe sittable substance` may be caused to passthrough the screen. n i

5. In a device ot the class described the combination with `a closedsitting chamber` comprising a screen body having a central apnertnre therein, an expansion chamber commu i nicating with the sitter chamber through the mesh ot the screen, means tor shutting oit communication between the expansion chamber and the central aperture in the screen and constituting a tailings `discharge port. means tor depositing a sittable substance upon the surface otthe screen interiorly ot the sitter chamber, means for intermittently directing a blast ot air through portions of the tscreen, into the sitter chamber, and means tor sup plying air under pressure to the last mentioned means and the depositing means and having a return connection with the expan sion chamber for maintaining a pressureva-` riation` between the sitter` and expansion chambers, the movement ot air under pressure serving to carry the sittable. substance through the mesh ot the screen and to move the tailings toward the central aperture in ile the screen for separating the sifted substance and tailings.

6. In a device of the class described the combination of a casing comprising an eX- pansion chamber, a sifter chamber communicating with the expansion chamber, a screen having a central aperture interposed between communicating portions of the sifter and ex'- pansion chambers, a combined air brush hold er and feed nozzle casting rotatably mounted in the expansion chamber and extending through the central aperture in the screen, an air brush secured to the air brush holder and adapted to move adjacent the lower face of the screen as the brush holder revolves, a distributor plate mounted above the central aperture in the screen and surrounding the feed nozzle, means for feeding a siftable substance to the distributor plate, a tailing box, means comprising a cylinder surrounding the air brush holder and forming a communicating passage between the central aperture in the screen and the tailing box, power means for imparting rotation to the brush holder and feed nozzle, and blower means for directing air under pressure to the air brush and feed nozzle, said blower means having an intake port communicating with the expansion chamber.

7 In a device of the class described the combination of a hollow stationary body member adapted to be placed in communication with a blower fan, a brush holder and feed nozzle member rotatably mounted upon said body member, a sifter chamber, a screen forming a bottom wall for the sifter chamber and having a central aperture therein for receiving the feed nozzle member, a grooved ring surrounding the central aperture in the screen, a cylinder secured to the brush holder and feed nozzle member and having a bearing upon the flange for providing communication between the central aperture in the screen and the exterior of the stationary body member, a casing surrounding the sifter chamber and the cylinder, an air brush communicating with the interior of the brush holder and feed nozzle, and secured to the cylinder and adapted to be moved with the cylinder about the ring fiange and to direct air under pressure through the screen into the sift-er chamber as it passes beneath the screen, scraper means secured to the cylinder and air brush for scraping the floor portion of the expansion chamber, and means comprising a plate surrounding the feed nozzle for positioning a quantity of siftable substance in front of the feed nozzle.

8. In a device of the class described the combination of an expansion chamber, a hollow body member mounted upon the boetom wall of the expansion chamber and adaptedto be connected to a source of forced air pressure, a brush holder and feed nozzle member rotatably mounted upon said body member and communicating with the interior thereof, an air brush secured to the brush holder and having communication therewith, a cylinder carried by the brush holder member, a sitter chamber comprising a screen bottom portion having a central aperture therein, the sifter chamber and expansion chamber having communication one with the other through the mesh ofthe screen, the cylinder serving to shut off free communication between the cent-ral aperture in the screen and the expansion chamber, feed supply means` having an adjustable outlet, a plate in the sifter cluunber disposed below said outlet and adapted to receive and position a siftable substance from the outlet and the feed means, and means for imparting rotation to the brush holder and feed nozzle.

9. In a device of the class described the combination of a sifter chamber comprising a screen bottom wall having a central aper4 ture therein, a distributor plate positioned above said aperture, means for depositing a siftable substance adjacent the edge of said plate, an expansion chamber communicating with the sitter chamber through the mesh of the screen, means for directing a blast of air across the distributor platefor scattering the siftable substance over the screen, and adapted to build up an increased air pressure in the sifter chamber, means connected with the last mentioned means for directing air under pressure into the sifter chamber from beneath the screen for placing the siftable substance in suspension in the sifter chamber and for moving the tailings of the siftable substance toward the central aperture in the screen, means for reducing air pressure in the expansion chamber whereby a flow of air under pressure is caused to pass from the sifter chamber into the expansion chamber for moving the suspended particles through the screen into the expansion chamber, and means for receiving the tailings as they drop through the central aperture in the screen under the influence of gravity.

l0. In a device of the class described the combination of an expansion chamber, a sifter chamber having a screen covered open ing communicating with the expansion chamber, mea-ns for distributing a siftable substance over the surface of the screen in the sifter chamber, an air brush adapted for movement across the face of the screen, to direct air under pressure through said screen and into the sifting chamber whereby a portion of the screen is cleared of siftable substance and whereby pressure is built up in the sifting chamber, and means to relieve pressure in the expansion chamber for per mitting the air under pressure in the sifter chamber to pass through the screen to carry the siftable substance into the expansion chamber.

ll. In a device of the class described the combination of an expansion chamber, a sitter chamber having a screen covered opening comn'iunicating With the expansion chamber, a tailing box, means for establishing communication between the tailing` box and sitter chamber, means for distributing a siftable substance over the screen Within the sifter cliainbei', an air brush in the expansion chamber and mounted for movement over the screen whereby to force air under pressure through the screen into the sifter chamber, such movement of air serving to clear the screen of siftable substance, to agitate said substance and to build up pressure in the sitter chamber whereby said air under pressure may pass through the screen into the expfnsion chamber and carry sift-able substance with it, the tailings of siftable substance being permitted to drop under the influence of gravity from the screen to the tailing box, and means `tor maintaining a reduced air pressure in the expansion chamber.

12. In a sifting device the combination of a screen member, means for depositing a siiitable substance upon one face of the screen, an air brush :tor movement across the opposed face of the screen, means for maintaining reduced air pressure on the last inentioned side of the screen whereby the siftable substance may be caused to pass through the screen, and means for removing tailings from the screen,

13. In a sitter the combination of a casing, a screen dividing the. casing into a pair of chambers, means for introducingr a siftable substance into one of the chambers and means for cleansing the screen of sift-able substance and for creatingr unequal air pressures in the chambers, the greater pressure being developed in the first mentioned of the pair oit' chambers, wheieby movement of air to the other of said. chambers carries the siftable substance through the screen. p

1i. In a sifter the combination of a casing, a screen having an opening therein, and

dividing the casing into a pair of chambers, a i

tailing box beneath the opening in the screen, means for introducing a siftable substance into one of said cham-bers and means for clearing the screen of siftable substance i chambers, a tailing box in open communi-` cation With one oi said chambers, means for introducing a siftable substance into said chamber and pneumatic means for agitating the siitable substance Within said chamber to effect movement of the siftable substance through the screen into the second chamber and to eilect movement of tailings of the siftable substance into the tailing box.` 16. In a sifter the combination of a closed casing, a stationary horizontal screen having an opening therein and dividing the casing into a pair of chambers, a tailing box beneath the. opening in the screen,`means for introducing a siftable substance into one of said chambers, and unitary means for agitating the siftable substance within, said chamber and clearing the screen of siftable substance to effect movementof the siftable i substance through the screen into the second chamber and to efectmovement of the tailings ot the siftable substance to the opening in the screen-` 17. A pneumatic sifter comprising a closed casing, a substantially horizontal screen extending across said casing to provide a pair of chambers, one of said chambers being adapted to receive a siftable substance and a moving pneumatic means in the second chamber for introducing a gaseous fluid under pressure through the screen for clearing the screen of siftable substance and for producing increased pressure in the first mentioned chamber whereby the hner particles of siftable substance are carried `through the screen into the second chamber.

In testimony whereof, I have hereunto subscribed my name this 17thday of February, 1926.

`sierMioNn sciiirr. 

